Alaska is burning as fires multiply by the hundred

Alaska is nearing the peak of its all-important tourist season, when the land of the "midnight sun" beckons cruise ship passengers and hiking enthusiasts with its mountains and abundant wildlife. Yet instead of sunny skies lasting late into the night, like June usually brings, the air over much of the state has been filled with eye-burning smoke, with more than 300 individual fires burning as of Thursday.

A handful of new large wildfires ignited on Wednesday, according to the National Interagency Fire Center (NIFC) in Boise, Idaho, which coordinates federal firefighting operations. Hundreds of firefighters are battling blazes across the state, attacking them from the land and the air, with a growing fleet of tanker aircraft streaming into the state from their bases in the Western U.S., Canada, and locally in Alaska.

The fires are connected to weather conditions dating back to the winter, when much of the state saw a profound lack of snow and unusually mild temperatures. The absence of snow cover starved the lands of much-needed moisture to fend off fires ignited by human activities, such as building campfires, and natural sources, like lightning.

A fire danger sign is set beyond the extreme level in the small town of Tetlin, Alaska, Thursday, June 18, 2015.

Following the anemic snow covering large swaths of the state came a warm spring, with May setting a record for the warmest such month the state has seen since records began there 91 years ago. The statewide average temperature for the month was 44.9 degrees Fahrenheit, which was 7.1 degrees above average. Barrow and Juneau both set records for the warmest such month.

Statewide average temperatures in Alaska during May, showing the record heat in May 2015.

Image: NOAA/NCEI

June is bringing little relief, with high temperatures nearing 70 degrees all the way to Barrow, the northernmost community in the U.S., which lies above the Arctic Circle.

Barrow had a record high temperature of 67 degrees on June 19, for example, which was 17 degrees above average for the date. Many other communities set or tied record highs between June 15 and 20, as they had during much of May.

The wildfires are burning across central and southern portions of the state, and have been increasing over time as summer thunderstorm season gets underway, touching off storms that deliver little rain but lots of lightning. These storms are known as dry thunderstorms, and they're a major cause of fires from Alaska to Canada and across the parched Western U.S.

The fires are far above average for this time of year, and are in keeping with a long-term trend toward more frequent fires and larger fires in the "Frontier State."

The high pressure area parked over Alaska (red area in upper left of map).

Image: WeatherBELL Analytics

Alaska continues to burn and smoke fills the skies. The first image was obtained from the VIIRS Polar Orbiter this...

The proximate cause of the heat and fires is a massive dome of high pressure extending from near the surface to high altitudes. This high, or heat dome, has extended its influence from the Bering Sea to the border between Alaska and Canada, hundreds of miles to the east. At times, the high has pumped mild air across interior Alaska on strong southwest winds.

At other times it has backed off a bit, allowing temperatures to cool, only to come roaring back at a greater intensity than before, parking itself across western Alaska in recent days. This has caused a northerly flow of dry, warm air to affect much of the state. Just enough atmospheric instability has been present to spark afternoon thunderstorms across the state's many mountain ranges, touching off new blazes.

The heat this year is not confined to Alaska. Record warmth is also gripping the Western U.S., setting off wildfires in California, while Siberia just had its warmest spring on record. Siberian fires as well as fires in parts of Alaska release higher amounts of carbon dioxide and other planet-warming emissions than fires in other parts of the U.S., because of the soil composition and presence of permanently frozen soil (permafrost).

Fires reflect a long-term trend

The unusually hot weather and widespread fires are becoming the norm in Alaska, as the state has warmed more than twice as fast as the rest of the country in the past 60 years, with about 3 degrees Fahrenheit of average warming overall, according to a report this week from the nonprofit research group Climate Central.

2004 was a bad fire year but look at MODIS Fire det. from June 30 of 2004 and compare that this year. Big difference. pic.twitter.com/H9PLHi4Ogm

The analysis found that the number of large wildfires, each burning 1,000 acres or more, increased in the 1990s. The past decade saw about twice as many large wildfires as were recorded during the 1950s and '60s. The area burned by wildfires in Alaska is also skyrocketing as temperatures warm, snow cover melts earlier in the year and weather patterns change.

Climate Central found that in two years, 2004 and 2005, wildfires burned a larger area than in the 15 years combined between 1950 and 1964.

Perhaps more importantly, researchers found that Alaska’s wildfire season is about 40% longer now than it was in the 1950s. The fire season is now about three months long, from May to August, which is more than a month longer than it used to be. In addition, fires are encroaching on areas that have been immune from them during colder times.

A study published in 2010, for example, found that central Arctic fires in tundra ecosystems have been burning at rates unprecedented in the past 5,000 years.

According to a federal climate report published in 2014, the area burned by wildfires in Alaska could double by 2050, and triple by 2100, if emissions of greenhouse gases, such as carbon dioxide, are not curtailed significantly.

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